In coating processes, such as for example internal alitizing processes (aluminizing of internal surfaces), the layer thickness is determined by way of a metallographic examination. For this purpose, a wire specimen is introduced into the coating process at a location which is representative of a component which is to be coated. After the coating process has ended, the wire specimen is removed and is then, expensively, cut open and examined. Each coating process is monitored and documented by the use of concomitant working specimens. These measuring and testing methods do not allow coating processes which are not to spec to be corrected as they are ongoing. Therefore, this is a very expensive form of quality assurance.